Phosphate esters dispersants

ABSTRACT

A dispersant which comprises the reaction product of a phosphating agent such as polyphosphoric acid and a compound of formula R—OH wherein R is a residue of a polyester and/or polyether having a polymerisation terminating group and where the ratio of each phosphorus atom of the phosphating agent to RO—H is from 1.3:1 to 3:1. The dispersants are thought to be pyrophosphates.

The present invention relates to phosphate esters of a polyester, theiruse as dispersants for dispersing a particulate solid in a liquid mediumand to millbases, paints and inks, including inks for ink jet printingcontaining such dispersants. The dispersants may also be used fordispersing a particulate solid in a plastics material.

Dispersants which are phosphate esters of a polyester having aterminating hydroxy group have been widely reported in the patentliterature. In certain patents, such as U.S. Pat. No. 4,746,462, U.S.Pat. No. 5,130,463 and U.S. Pat. No. 5,300,255, the dispersant has beenaccorded a specific structure wherein from 1 to 3 of the hydroxy groupsin a phosphate group are replaced by the residue of a polyester having aterminating hydroxy group. In other patent documents such as WO97/19748, WO 97/19948, WO 97/42252, WO 98/19784, WO 99/49963, WO99/55762 and WO 01/80987, the dispersant is defined as a phosphate esterof a defined polyester having a terminating hydroxy group. Morespecifically, the dispersants are defined wherein the ratio of polyesterto each phosphorus atom of the phosphating agent is from 1:1 to 3:1which, therefore, again clearly describes replacing from 1 to 3 of thehydroxy groups of the phosphate group. In all cases the dispersant canbe a mixture of mono-, di- and tri-phosphate.

It has now been found that where the dispersant is prepared by using anexcess of the phosphating agents, such as polyphosphoric acid, relativeto the polyester having a terminating hydroxy group it exhibits superiorproperties such as lower millbase viscosity, higher pigment loading,superior flocculation resistance and better stability of millbases,paints and inks. Furthermore, the paint films often exhibit superiorgloss, haze and colour strength and, in the case of transparent ironoxides, the paint films often exhibit higher transparency.

The precise structure of the phosphate dispersants has not been whollyelucidated but it is thought to involve polyphosphorus moieties whichmay include pyrophosphates.

According to the invention there is provided a dispersant (hereinafterThe Dispersant) which comprises the reaction product of a phosphatingagent and a compound of formula 1R—OH  1wherein the ratio of each atom of phosphorus in the phosphating agent tothe compound of formula 1 is not less than 1.3:1, including mixtures andsalts thereof;wherein

R is the residue of a polyester and/or polyether having a polymerisationterminating group.

Preferably, the ratio of each phosphorus atom of the phosphating agentto each compound of formula 1 is not less than 1.5:1 and especially notless than 1.8:1. Although the amount of phosphating agent may beconsiderably in excess of the amount of compound of formula 1 there isgenerally no additional benefit and consequently it is preferable thatthe ratio of each phosphorus atom of the phosphating agent to thecompound of formula 1 is not greater than 5:1, more preferably notgreater than 3:1 and especially not greater than 2.5:1.

When R is the residue of a polyester and polyether it may be a randomcopolymer but it is preferably a block copolymer and the phosphatingagent may react with a hydroxy group attached to either an ether orester residue.

The weight-average molecular weight of R—OH can vary over a wide rangedepending on the nature of the liquid medium in which the dispersant isto be used. Preferably, the number-average molecular weight of R—OH isnot less than 200, more preferably not less than 300 and especially notless than 500. It is also preferred that the number-average molecularweight of R—OH is not greater than 10,000, more preferably not greaterthan 5,000 and especially not greater than 3,000. The molecular weightof R—OH is largely dependant on the end-use of the dispersant and highermolecular weights are preferred when the dispersant is used to dispersea particulate solid in a non-polar liquid medium. Conversely, lowermolecular weights of R—OH are preferred when the dispersant is used todisperse a particulate solid in a polar liquid medium; especially wherethe liquid medium is water, an aqueous-based liquid medium or plasticsmaterial.

The polyester and/or polyether moiety of R—OH may be attached to thepolymerisation terminating group via an amino, mercaptan or preferably ahydroxy group.

The compound of formula I is preferably a compound of formula 2.TO—(CO-A-O)_(n)(B-O)_(m) H  2wherein

T is a polymerisation terminating group;

A is C₁₋₃₀-alkylene or C₂₋₃₀-alkenylene;

B is C₂₋₆-alkylene;

n and m are each, independently, from 0 to 500; and

n+m is not less than 4;

including salts and mixtures thereof.

The group (CO-A-O)_(n) may be the residue of a single hydroxy carboxylicacid or lactone thereof or it may be the residue of two or moredifferent hydroxy carboxylic acids or lactones thereof. Similarly thegroup (B-O)_(m) may be the residue of a single alkylene oxide or it maybe the residue of two or more different alkylene oxides.

The compound of formula 2 is herein after referred to as a TPE alcohol.

The polymerisation terminating group is preferably the residue of anorganic hydroxy compound, T-OH. T may be aryl, heteroaryl, aralkyl,cycloalkyl or alk(en)yl, which may be linear or branched.

Preferably, T contains not greater than 50 and especially not greaterthan 30 carbon atoms and may carry substitutents. The nature of Tdepends on the end-use of the dispersant. Thus, when the dispersant isused to disperse a particulate solid in a non-polar liquid medium thenumber of carbon atoms in T-OH is preferably not less than 8 andespecially not less than 14. When the dispersant is used to disperse aparticulate solid in a polar medium the number of carbon atoms in T-OHis preferably not greater than 14 and especially not greater than 10.When the dispersant is to be used to disperse a particulate solid in anaqueous, or predominantly aqueous, liquid medium the number of carbonatoms in T-OH is preferably not greater than 10. When the liquid mediumis, or contains, water, T is preferably alkyl, more preferablyC₁₋₈-alkyl and especially C₁₋₄-alkyl and may be linear or branched.

The choice of T-OH is also influenced by the nature of the groups(CO-A-O)_(n) and (B-O)_(m) in order to render the dispersant compatiblewith the liquid medium depending on its polarity.

When T is aryl it may be polycyclic but is preferably naphthyl or phenyland it may carry substitutents such as halogen, aryloxy, alkoxy, alkyland styryl. Halogen may be fluorine, bromine and especially chlorine.Alkoxy is preferably C₁₋₁₈-alkoxy and may be linear or branched. Alkylis preferably C₁₋₁₄-alkyl and may be linear or branched. Aryloxy ispreferably phenoxy. Halogen is preferably fluorine, bromine andespecially chlorine.

Specific examples of T-OH where T is aryl are phenol, 1-naphthol,2-naphthol, 4-nonylphenol, 2-phenoxyphenol and 4-phenoxyphenol.2-Naphthol is preferred.

When T is heteroaryl, it is preferably thienyl.

When T is aralkyl, it is preferably benzyl or 2-phenylethyl.

When T is cycloalkyl it is preferably C₃₋₈-cycloalkyl such ascyclopropyl, cyclopentyl and especially cyclohexyl optionallysubstituted by C₁₋₆-alkyl.

When T is alkyl it is preferably C₁₋₃₆-alkyl and may be linear orbranched. Examples of T are methyl, ethyl, n-propyl, isopropyl, n-butyl,tert-butyl, n-hexyl, n-heptyl, n-octyl, 2-ethylbutyl 2-ethylhexyl,n-nonyl, n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl, n-octadecyl,3-heptyl, 3,5,5-trimethylhexyl, 3,7-dimethyloctyl and the residue of aso-called Guerbet alcohol such as those which are commercially availableunder the trade name Isofol (ex Condea GmbH) including mixtures thereof.Specific examples of Guerbet alcohols are Isofol 12, 14T, 16, 18T, 18E,20, 24, 28, 32T and 36.

When T is alkenyl it preferably contains not less than 4 and especiallynot less than 8 carbon atoms such as oleyl.

When T is alkyl it may be substituted by C₁₋₆-alkoxy or halogen such asfluorine and chlorine. However, it is preferred that T is unsubstitutedalkyl.

It is preferred, generally, that T is alkyl which may be linear orbranched and is especially C₁₋₂₀-alkyl.

When A is alk(en)ylene it may be linear or branched and includesmixtures. The choice of hydroxy carboxylic acid or lactone from which(CO-A-O) is derived depends on the end use of the dispersant. Thus,where the dispersant is intended to disperse a particulate solid in anon-polar liquid medium, A preferably contains not less than 8 carbonatoms. When the dispersant is intended to disperse a particulate solidin a polar liquid medium, A preferably contains not greater than 10,more preferably not greater than 8 and especially not greater than 6carbon atoms. The alk(en)ylene group may also be substituted, especiallyby C₁₋₆-alkyl groups which may be linear or branched. Examples ofhydroxy carboxylic acids from which (CO-A-O)_(n) is derived are glycolicacid, 5-hydroxyvaleric acid, 6-hydroxy hexanoic acid, ricinoleic acid,12-hydroxystearic acid, 12-hydroxy dodecanoic acid, 5-hydroxy dodecanoicacid, 5-hydroxy decanoic acid and 4-hydroxy decanoic acids. Examples oflactones from which (CO-A-O) is derived are β-propiolactone,δ-valerolactone, ε-caprolactone and the C₁₋₆-alkyl substitutedε-caprolactone derivatives such as 7-methyl, 3-methyl, 6-methyl,4-methyl, 5-methyl, 5-tert-butyl, 4,6,6-trimethyl and 4,4,6-trimethylε-caprolactone, including mixtures thereof. ε-Caprolactone,δ-valerolactone and 7-methyl ε-caprolactone are the preferred lactones.

Preferably, (CO-A-O)_(n) is derivable from one or two different hydroxycarboxylic acids or lactones thereof. Particularly useful dispersantsare those where (CO-A-O)_(n) is derived from 12-hydroxystearic acidoptionally in combination with ε-caprolactone, ricinoleic acidoptionally in combination with ε-caprolactone and ε-caprolactoneoptionally in combination with either glycolic acid or δ-valerolactone.

When the group (CO-A-O)_(n) is derivable from a mixture ofε-caprolactone together with glycolic acid, δ-valerolactone and/or alkylsubstituted ε-caprolactone the ε-caprolactone is preferably present inmolar excess relative to the other lactone(s).

When B is C₂₋₆-alkylene it may be linear or branched and is especiallyC₂₋₄-alkylene. Preferably (BO) is the residue of an alkylene oxide suchas ethylene oxide (EO), propylene oxide (PO) or butylene oxide (BuO),including mixtures thereof. When (BO)_(m) is derived from two or moredifferent alkylene oxides the copolymer may be a random or preferablyblock polymer. When the residue (B-O)_(m) is or contains BuO as repeatunit it is preferably derived from poly(tetrahydrofuran). The choice ofalkylene oxide depends largely on the intended end-use of thedispersant. Thus, when the dispersant is intended to disperse aparticulate solid in a polar liquid medium, such as water, it ispreferred that (BO)_(m) is derived from EO, optionally containing up to20 mole % PO. When the dispersant is intended to disperse a particulatesolid in a non-polar liquid medium the group (BO)_(m) is preferablyderived from BuO or preferably PO optionally containing up to 20 mole %EO.

It will be obvious to the skilled addressee that variants on thepolyester/polyether chain represented by (CO-A-O)_(n) (BO)_(m) may bemade where repeat units represented by (BO) interrupt the chainrepresented by (CO-A-O)_(n) and/or repeat units represented by (CO-A-O)interrupt the chain represented by (BO)_(m). Such variants also fallwithin the scope of the present invention.

The polyether chain represented by (BO)_(m) may also contain ester orurethane groups where it is desirable to build the (BO)_(m) polyetherchain from smaller polymers or oligomers which may be the same ordifferent. For example, the polyether chain represented by (BO)_(m) maybe made by joining the two polyether chain segments by reaction with adicarboxylic acid or anhydride or a polyisocyanate such as adiisocyanate. Examples of such dicarboxylic acids, anhydrides orisocyanates are 1,6-hexyldicarboxylic acid, terephthalic acid, phthalicanhydride, 1,6-hexyl diisocyanate and tolyl diisocyanate. Preferably,the chain segment represented by (BO)_(m) is free from the residue of adicarboxylic acid or isocyanate.

The polyether chain represented by (BO)_(m) may be directly attached tothe polymerisation terminating group. Examples of such polyethers arepolyethylene glycol mono C₁₋₁₀-alkyl ethers, preferably the mono methylethers, more preferably those mono-alkyl ethers having a number averagemolecular weight of less than 3000 and especially those having amolecular weight of less than 2000. Monoalkyl ethers having a numberaverage molecular weight which is less than 1500 are especially useful.Other examples are the mono-alkyl ethers of polypropylene glycol and themono alkyl ethers of polyethylene glycol/polypropylene copolymers wherethe alkyl group may be attached to either a PO or EO residue.

The ratio of n:m may vary over a wide range depending on the intendeduse of the dispersant. Thus, when the dispersant is intended fordispersing a particulate solid in an aqueous or predominantly aqueousliquid medium in one preferred class of dispersants n is zero and m ispreferably not greater than 100. Particularly important dispersants foraqueous media are where TO- is the residue of 2-naphthol, alkylphenol,styrenated phenol or phenyl phenol. In another preferred class ofdispersants for use in aqueous or predominantly aqueous liquid media(CO-A-O) is derived from ε-caprolactone optionally in admixture withδ-valerolactone, BO is the residue of ethylene oxide and the molecularweight of TO-(CO-A-O)_(n) is less than the molecular weight of (BO)_(m).Particularly important dispersants of this class for use in aqueousliquid media are those derived from ethylene glycol monomethyl ether andparticularly those where m+n is not greater than 200 and especially notgreater than 100.

One important class of dispersants for use in polar liquid media otherthan water is where m is zero, (CO-A-O)_(n) is derived fromε-caprolactone optionally in admixture with glycolic acid and/orδ-valerolactone and where n is preferably not greater than 100, morepreferably not greater than 50 and especially not greater than 20.Another important class of dispersant for use in polar liquid media iswhere (CO-A-O)_(n) is derived from ε-caprolactone optionally inadmixtiure with glycolic acid and/or δ-valerolactone, BO is derived fromethylene oxide and/or propylene oxide and where the molecular weight ofRO(CO-A-O)_(n) is greater than the molecular weight of (BO)_(m), m+n ispreferably not greater than 100 and especially not greater than 50.Particularly important dispersants of this class are those derived froma polyethylene glycol mono alkyl ether reacted with ε-caprolactoneoptionally in the presence of glycolic acid and/or δ-valerolactone.

When the dispersant is intended for use in a non-polar liquid media animportant class of dispersant is those where (BO)_(m) is derived from POand/or BuO. A particularly preferred class of dispersant for use innon-polar liquid media is where m is zero and (CO-A-O)_(n) is derivedfrom a C₈₋₂₄-alk(en)yl hydroxy carboxylic acid such as 12-hydroxystearicor ricinoleic acid optionally containing ε-caprolactone.

In general, monohydric alcohols of formula R—OH which can be used tomake dispersants according to the invention may be any of thosedisclosed in U.S. Pat. No. 4,746,462, U.S. Pat. No. 5,130,463, U.S. Pat.No. 5,300,255, WO 97/19748, WO 97/19948, WO 97/42252, WO 98/19784, WO99/49963, WO 99/55762 and WO 01/80987. These are all incorporated hereinby reference.

The compounds of formula 1 which are used to make the dispersantsaccording to the invention may be made by any method known to the art.This includes reacting a polymerisation terminating compound such asT-OH under anhydrous conditions with one or more alkylene oxides,preferably in an inert atmosphere and preferably in the presence of analkaline catalyst or a Lewis acid catalyst. The polyether so obtainedmay optionally be reacted with one or more hydroxy carboxylic acids orlactones thereof preferably in an inert atmosphere and preferably in thepresence of an esterfication catalyst to give a polyether/polyesterblock copolymer where the polymerisation terminating group is attachedto the polyether moiety. Alternatively, the polymerisation terminatingcompound may be first reacted with one or more hydroxy carboxylic acidsor lactones thereof to give a polyester having a terminatingpolymerisation group and this polyester may then be optionally reactedwith one or more alkylene oxides. The conditions required for making thepolyester are described inter alia in WO 98/19784 and WO 01/80987.

The reaction between the compound of formula 1 and the phosphating agentis typically carried out at a temperature from 40° C. to 120° C.,preferably in an inert atmosphere or optionally in an inert solvent.Preferably, the temperature is above 60° C. and especially above 80° C.In order to minimise discoloration of the dispersant the temperature ispreferably not greater than 100° C.

Thus, according to a further aspect of the invention there is provided aprocess for making a phosphate ester dispersant which comprises reactinga compound of formula 1 with a phosphating agent at a temperature from40° C. to 120° C. characterised in that the ratio of each phosphorusatom of the phosphating agent to the compound of formula 1 is not lessthan 1.3:1. The ratio of each phosphorus atom of the phosphating agentto the compound of formula 1 is preferably not greater than 5:1 and morepreferably not greater than 3:1 and especially not greater than 2.5:1.

Examples of phosphating agents are POCl₃, P₂O₅ and especiallypolyphosphoric acid.

Examples of suitable inert solvents are aliphatic hydrocarbons such asoctane, petroleum ethers, ligroin, mineral spirits and kerosene;aromatic hydrocarbons such as benzene, toluene and xylene; halogenatedaliphatic hydrocarbons such as trichloroethane, tetrachloroethane andaromatic chlorinated hydrocarbons such as di- and tri-chlorobenzene. Itis preferred, however, that the reaction between the compound of formula1 and the phosphating agent is carried out in the absence of an inertsolvent.

The inert atmosphere may be provided by any one of the inert gases ofthe Periodic Table but is preferably nitrogen.

When the phosphating agent is POCl₃, it is preferable to carry out thereaction with the compound of formula 1 in the presence of an organicbase, for example a tertiary amine such as triethylamine, pyridine,2,6-lutidine or 1,8-diaza-bicyclo-(5.4.0) undec-7-ene.

As disclosed hereinbefore, the dispersants according to the inventionmay be present in the form of a salt which may be the salt of aninorganic or organic cation. Examples of suitable inorganic cations arethe alkali metals such as sodium, potassium and lithium and the alkaliearth metals such as calcium, barium and magnesium. The dispersant mayalso be present in the form of an ammonium salt. Examples of organiccations are primary, secondary and tertiary mono- and poly-amines,especially those containing from 1 to 30 carbon atoms such asmethylamine, ethylamine, propylamine, butylamine, hexlamine, octylamine,2-ethylhexylamine, dodecylamine, octadecylamine, oleylamine,diethylamine, dibutylamine, distearylamine, triethylamine,tributylamine, dimethyloctylamine, dimethyidecylamine,dimethyldodecylamine, dimethyl-tetradecylamine, dimethylhexadecylamine,dimethyloctadecylamine, dimethyloleylamine, dilauryl monomethylamine,trioctylamine, dimethylaniline, ethylenediamine, propylenediamine,hexamethyldiamine and stearylpropylene diamine; quaternary ammoniumcations such as octadecyl trimethyl ammonium and dioctadecyl dimethylammonium; and alkanolamine such as ethanolamine, diethanolamine,triethanolamine, dimethylethanolamine, diethyl ethanolamine,propanolamine and ethoxylates of fatty amines, including mixtures ofamines. The choice of salt depends largely on the nature of theparticulate solid and the nature of the liquid medium. Where the liquidmedium is water or a polar liquid medium and the particulate solid is apigment, useful effects have been obtained where the dispersant is asalt of diethanolamine.

The dispersant may also be subsequently reacted with an organic hydroxycompound to form a mixed ester. Examples of suitable hydroxy compoundsare C₁₋₃₀-aliphatic alcohols such as ethanol, butanol, hexanol, decanol,dodecanol, cetyl alcohol, oleyl alcohol and stearyl alcohol, includingmixtures thereof. It is, however, preferred that the dispersant is notsubsequently reacted with an organic hydroxy compound.

The preparation of the salt or reaction with an organic hydroxy compoundmay be carried out under similar conditions to the reaction between thecompound of formula 1 and the phosphating agent and may be carried outwithout prior isolation of the reaction product of the compound offormula 1 and phosphating agent.

As noted hereinbefore, the dispersants are particularly useful fordispersing a particulate solid in a liquid medium.

According to a further aspect of the invention there is provided acomposition comprising a particulate solid and The Dispersant.

According to a still further aspect of the invention there is provided adispersion comprising a The Dispersant, a particulate solid and a liquidmedium.

The solid present in the dispersion may be any inorganic or organicsolid material which is substantially insoluble in the liquid medium atthe temperature concerned and which it is desired to stabilise in afinely divided form therein.

Examples of suitable solids are pigments for solvent inks; pigments,extenders and fillers for paints and plastics materials; dyes,especially disperse dyes; optical brightening agents and textileauxiliaries for solvent dyebaths, inks and other solvent applicationsystems; solids for oil-based and invert-emulsion drilling muds; dirtand solid particles in dry cleaning fluids; particulate ceramicmaterials; magnetic materials and magnetic recording media, fireretardants such as those used in plastics materials, metal salts such ascarbonates and oxides which are used in the cement industry andbiocides, agrochemicals and pharmaceuticals which are applied asdispersions in organic media.

A preferred solid is a pigment from any of the recognised classes ofpigments described, for example, in the Third Edition of the ColourIndex (1971) and subsequent revisions of, and supplements thereto, underthe chapter headed “Pigments”. Examples of inorganic pigments aretitanium dioxide, zinc oxide, Prussian blue, cadmium sulphide, ironoxides, vermilion, ultramarine and the chrome pigments, includingchromates, molybdates and mixed chromates and sulphates of lead, zinc,barium, calcium and mixtures and modifications thereof which arecommercially available as greenish-yellow to red pigments under thenames primrose, lemon, middle, orange, scarlet and red chromes. Examplesof organic pigments are those from the azo, disazo, condensed azo,thioindigo, indanthrone, isoindanthrone, anthanthrone, anthraquinone,isodibenzanthrone, triphendioxazine, quinacridone and phthalocyanineseries, especially copper phthalocyanine and its nuclear halogenatedderivatives, and also lakes of acid, basic and mordant dyes. Carbonblack, although strictly inorganic, behaves more like an organic pigmentin its dispersing properties. Preferred organic pigments arephthalocyanines, especially copper phthalocyanines, monoazos, disazos,indanthrones, anthranthrones, quinacridones and carbon blacks.

Other preferred solids are: extenders and fillers such as talc, kaolin,silica, barytes and chalk; particulate ceramic materials such asalumina, silica, zirconia, titania, silicon nitride, boron nitride,silicon carbide, boron carbide, mixed silicon-aluminium nitrides andmetal titanates; particulate magnetic materials such as the magneticoxides of transition metals, especially iron and chromium, e.g.gamma-Fe₂O₃, Fe₃O₄, and cobalt-doped iron oxides, calcium oxide, calciumcarbonate, magnesium carbonate, ferrites, especially barium ferrites;and metal particles, especially metallic iron, nickel, cobalt and alloysthereof; agrochemicals such as the fungicides flutriafen, carbendazim,chlorothalonil and mancozeb and fire retardants such as aluminiumtrihydrate and magnesium hydroxide.

It is especially preferred that the particulate solid is an inorganicpigment, extender or filler.

The liquid may be water or an organic medium, including mixturesthereof.

The organic medium present in the dispersions of the invention ispreferably a polar organic medium or a substantially non-polar aromatichydrocarbon or halogenated hydrocarbon. By the term “polar” in relationto the organic medium is meant an organic liquid or resin capable offorming moderate to strong bonds as described in the article entitled “AThree Dimensional Approach to Solubility” by Crowley et al in Journal ofPaint Technology, Vol. 38, 1966, at page 269. Such organic mediagenerally have a hydrogen bonding number of 5 or more as defined in theabovementioned article.

Examples of suitable polar organic liquids are amines, ethers,especially lower alkyl ethers, organic acids, esters, ketones, glycols,alcohols and amides. Numerous specific examples of such moderatelystrongly hydrogen bonding liquids are given in the book entitled“Compatibility and Solubility” by Ibert Mellan (published in 1968 byNoyes Development Corporation) in Table 2.14 on pages 39-40 and theseliquids all fall within the scope of the term polar organic liquid asused herein.

Preferred polar organic liquids are dialkyl ketones, alkyl esters ofalkane carboxylic acids and alkanols, especially such liquids containingup to, and including, a total of 6 carbon atoms. As examples of thepreferred and especially preferred liquids there may be mentioneddialkyl and cycloalkyl ketones, such as acetone, methyl ethyl ketone,diethyl ketone, di-isopropyl ketone, methyl isobutyl ketone, di-isobutylketone, methyl isoamyl ketone, methyl n-amyl ketone and cyclohexanone;alkyl esters such as methyl acetate, ethyl acetate, isopropyl acetate,butyl acetate, ethyl formate, methyl propionate, methoxy propylacetateand ethyl butyrate; glycols and glycol esters and ethers, such asethylene glycol, 2-ethoxyethanol, 3-methoxypropylpropanol,3-ethoxypropylpropanol, 2-butoxyethyl acetate, 3-methoxypropyl acetate,3-ethoxypropyl acetate and 2-ethoxyethyl acetate; alkanols such asmethanol, ethanol, n-propanol, isopropanol, n-butanol and isobutanol anddialkyl and cyclic ethers such as diethyl ether and tetrahydrofuran.

The substantially non-polar, organic liquids which may be used, eitheralone or in admixture with the aforementioned polar solvents, arearomatic hydrocarbons, such as toluene and xylene, aliphatichydrocarbons such as hexane, heptane, octane, decane, petroliumdistillates such as white spirit, mineral oils, vegetable oils andhalogenated aliphatic and aromatic hydrocarbons, such astrichloro-ethylene, perchloroethylene and chlorobenzene.

Examples of suitable polar resins, as the medium for the dispersion formof the present invention, are film-forming resins such as are suitablefor the preparation of inks, paints and chips for use in variousapplications such as paints and inks. Examples of such resins includepolyamides, such as Versamid™ and Wolfamid™, and cellulose ethers, suchas ethyl cellulose and ethyl hydroxyethyl cellulose. Examples of paintresins include short oil alkyd/melamine-formaldehyde,polyester/melamine-formaldehyde, thermosettingacrylic/melamine-formaldehyde, long oil alkyd and multi-media resinssuch as acrylic and urea/aldehyde.

The resin may also be a plastics material such as an unsaturatedpolyester resin including the so-called sheet moulding compounds andbulk moulding compounds which may be formulated with reinforcing fibresand fillers. Such moulding compounds are described in DE 3,643,007 andthe monograph by P F Bruins entitled “Unsaturated Polyester Technology”,Gordon and Breach Science publishers, 1976, pages 211 to 238. Examplesof polyester resins are those where an unsaturated polyester resin iscopolymerised with polystyrene or styrene-butadiene copolymer andespecially those containing calcium carbonate, magnesium oxide oraluminium hydroxide. The resin may also be an acrylic, styrene-acrylicor urethane-acrylic resin.

If desired, the dispersions may contain other ingredients, for exampleresins (where these do not already constitute the organic medium)binders, fluidising agents (such as those described in GB-A-1508576 andGB-A-2108143), anti-sedimentation agents, plasticisers, levelling agentsand preservatives.

The dispersions typically contain from 5 to 95% by weight of the solid,the precise quantity depending on the nature of the solid and thequantity depending on the nature of the solid and the relative densitiesof the solid and the organic medium. For example, a dispersion in whichthe solid is an organic material, such as an organic pigment, preferablycontains from 15 to 60% by weight of the solid whereas a dispersion inwhich the solid is an inorganic material, such as an inorganic pigment,filler or extender, preferably contains from 40 to 90% by weight of thesolid based on the total weight of dispersion.

The dispersion is preferably prepared by milling the solid in theorganic liquid at a temperature which is not greater than 40° C. andespecially not greater than 30° C.

The dispersion may be obtained by any of the conventional methods knownfor preparing dispersions. Thus, the solid, the liquid medium and TheDispersant may be mixed in any order, the mixture then being subjectedto a mechanical treatment to reduce the particles of the solid to anappropriate size, for example by ball milling, bead milling, gravelmilling or plastic milling until the dispersion is formed.Alternatively, the solid may be treated to reduce its particle sizeindependently or in admixture with either the liquid medium or TheDispersant, the other ingredient or ingredients then being added and themixture being agitated to provide the dispersion.

If the composition is required in dry form, the liquid medium ispreferably volatile so that it may be readily removed from theparticulate solid by a simple separation means such as evaporation. Itis preferred, however, that the dispersion comprises the liquid medium.

If the dry composition consists essentially of The Dispersant and theparticulate solid, it preferably contains at least 0.2%, more preferablyat least 0.5% and especially at least 1.0% dispersant based on weight ofthe particulate solid. Preferably the dry composition contains notgreater than 100%, preferably not greater than 50%, more preferably notgreater than 20% and especially not greater than 10% by weight based onthe weight of the particulate solid.

As described hereinbefore, the dispersants of the invention areparticularly suitable for preparing mill-bases where the particulatesolid is milled in a liquid medium in the presence of both a particulatesolid and a film-forming binder resin.

Thus, according to a still further aspect of the invention there isprovided a millbase comprising a particulate solid, The Dispersant and afilm-forming binder resin.

Typically, the millbase contains from 20 to 70% by weight particulatesolid based on the total weight of the mill-base. Preferably, theparticulate solid is not less than 30 and especially not less than 50%by weight of the mill-base.

The amount of resin in the mill-base can vary over wide limits but ispreferably not less than 10%, and especially not less than 20% by weightof the continuous/liquid phase of the mill-base. Preferably, the amountof resin is not greater than 50% and especially not greater than 40% byweight of the continuous/liquid phase of the mill-base.

The amount of dispersant in the mill-base is dependent on the amount ofparticulate solid but is preferably from 0.5 to 5% by weight of themill-base.

Dispersions and mill-bases containing the dispersants of the inventionare particularly suitable for use in paints, especially high solidpaints, inks, especially flexographic, gravure and screen inks, inks fornon-impact ink jet printing, and non-aqueous ceramic processes,especially tape-coating, doctor blade, extrusion and injection mouldingtype processes.

The Dispersants may also be used in paper making and as a thinner inaqueous hydraulic binders such as cements, plaster, calcium sulphate,calcium carbonate, calcium oxide, to give more dense structures afterhardening of the hydraulic binder. The Dispersants may also be used inmaking ceramics, electronic devices such as resistors and capacitors, asfluidisers in drilling muds, as detergents in dirt removal especially inthe textile coloration and cleaning industry and also for metal cleaningand rust conversion/prevention.

The invention is further illustrated by the following examples whereinall references to amounts are in parts by weight unless indicated to thecontrary.

EXAMPLE 1 Do 1, Cap 9.5, Val 3.5 1:2P, DEA

Dodecanol (11.86 parts, 0.064M ex Aldrich), ε-caprolactone (69.0 parts,0.604M ex Aldrich) and δ-valerolactone (22.3 parts, 0.227M ex Fluka)were stirred together at 150° C. under nitrogen. Zirconium butylate (0.3parts ex Fluka) was added and the reactants were stirred under nitrogenfor 6 hours at 185-190° C. The resultant pale yellow liquid was cooledto 90-95° C. Polyphosphoric acid (10.76 parts, 83% w/w P₂O₆ ex Aldrich)was added and the reactants were stirred under nitrogen for 6 hours at90-95° C. giving a yellow liquid which formed a beige wax at 25° C. (110parts). The beige wax had an Acid Value of 68.2 mg KOH/gm.

The above beige wax (50 parts) was stirred under nitrogen at 90-95° C.for 6 hours with diethanolamine (6.07 parts) giving a clear viscousliquid which, after cooling at 25° C., gave a cream wax (55 parts). Thisis Dispersant 1.

COMPARATIVE EXAMPLE A Do 1, Cap 9.5, Val 3.5 1.35:1P, DEA

The dodecanol, ε-caprolactone, δ-valerolactone polyester was prepared asdescribed in Example 1. This polyester (35 parts) and polyphosphoricacid (1.37 parts, 83% w/w P₂O₅) were stirred under nitrogen for 6 hoursat 90-95° C. The resultant phosphate ester had an Acid Value of 26.60 mgKOH/gm. Diethanolamine (1.70 parts) was added and the reaction wascontinued by stirring under nitrogen for 2 hours at 90-95° C. Thediethanolamine salt of the phosphate ester was obtained as a soft whitesolid after cooling to 25° C. (35 parts). This is Dispersant A.

EXAMPLE 2 Oc 1, Cap 11 1:2P

Octanol (6.22 parts, 0.048M ex Aldrich) and ε-caprolactone (60 parts,0.53M ex Aldrich) were stirred under nitrogen at 150° C. Zirconiumbutylate (0.3 parts ex Fluka) was added and the reactants were stirredunder nitrogen for 10 hours at 175-180° C. After cooling to 25° C., thepolyester was obtained as a white wax (65 parts).

The above white wax (30 parts) and polyphosphoric acid (3.7 parts 83%w/w P₂O₅) were stirred at 90-95° C. under nitrogen for 6 hours giving agolden liquid which on cooling to 25° C. formed a beige wax (33 parts)having an Acid Value of 77.68 mg KOH/gm. This is Dispersant 2.

COMPARATIVE EXAMPLE B Oc 1, Cap 11 1.35:1P

The polyester white wax from Example 2 (30 parts) was stirred undernitrogen for 6 hours at 90-95° C. together with polyphosphoric acid(1.37 parts, 83% w/w P₂O₅). This gave a clear liquid which after coolingto 25° C. formed a white wax (31 parts) with an Acid Value of 33.43 mgKOH/gm. This is Dispersant B.

EXAMPLES 3 and 4 WITH COMPARATIVE EXAMPLES C AND D

The dispersant (0.25 parts) was dissolved in a 4:1 mixture ofmethoxypropylacetate and n-butanol (6.75 parts) with warming asnecessary. After cooling to 20° C., 3 mm diameter glass beads (17 parts)and transparent iron oxide pigment (3 parts Sicotrans Red L2817 ex BASF)were added. The pigment was dispersed by shaking for 16 hours on ahorizontal shaker after which the beads were separated and the viscosityof the dispersion was assessed by manual shaking using an arbitraryscale of A to E (good to poor). The results are given in Table 1 below.TABLE 1 Example Dispersant Viscosity 3 1 A C A C 4 2 A D B B/C

When Examples 3 and C were repeated except using 3.5 parts red pigmentand 6.25 parts solvent mixture in place of the amounts used in these twoExamples the viscosity values were A and D, respectively.

EXAMPLES 5 AND 6 AND COMPARATIVE EXAMPLES E AND F

Examples 3, 4, C and D were repeated except using 0.15 parts dispersant,7.5 parts white pigment (Tioxide TR 92) and 2.35 parts solvent mixturein the place of the red pigment and amounts used in Examples 3 and 4.The results are given in Table 2 below. TABLE 2 Example DispersantViscosity 5 1 A E A B 6 2 A/B F B B/C

Example 5 was repeated except using 0.2 parts Dispersant A, 7.5 parts ofTioxide TR 92 and 2.3 parts mixed solvent and was compared with adispersion wherein the 0.2 parts of Dispersant A was replaced with 0.19parts Dispersant A with 0.01 parts orthophosphoric acid. It was alsocompared with a dispersion containing 0.19 parts Dispersant A, 0.01 partpolyphosphoric acid, 8.0 parts Tioxide TR 92 and 2.3 parts mixedsolvent. In all three cases the viscosity of the dispersion was assessedas B. These data indicate that the improved dispersion properties of thedispersants is not attributable to the presence of free phosphoric acidor free polyphosphoric acid.

Preparation of Polyalkylene Glycol Mono Alkyl Ethers

The following mono alkyl ethers were prepared using the method describedin EP 863795. Intermediate 1 MeO PEG (350) + 2PO 2 MeO PEG (550) + 3PO 3MeO PEG (550) + 4PO 4 MeO PEG (750) + 3PO 5 MeO PEG (750) + 5PO 6 MeOPEG (750) + 8PO 7 MeO PEG (2000) + 5PO

PEG represents a polyethylene glycol chain where the appropriate numberaverage molecule weight is given in parentheses. PO represents propyleneoxide where the preceding number indicates the number of repeat units.

Preparation of Polyether Dispersant EXAMPLE 7 MeO PEG (350)+2PO 1:2P

Intermediate 1 (70 parts; 0.15M) and polyphosphoric acid (83% P₂O₅,0.181M, ex Fluka) were stirred at 90-95° C. under nitrogen for 6 hoursto give a dark brown liquid (92 parts). This is Dispersant 3. The ratioof phosphorous atoms to each polyester chain is 2:1.

EXAMPLES 8 TO 13

Example 7 was repeated except using different polyether chains asindicated in Table 3 below where the ratio of phosphorus atoms in thephosphating agent to polyether chain is as indicated. TABLE 3 Inter-Dis- Ratio of P to Example mediate persant Polyether chain Polyether 8 24 MeO PEG (550) + 3PO 2.86:1   9 3 5 MeO PEG (550) + 4PO 2.67:1   10 4 6MeO PEG (750) + 3PO 2:1 11 5 7 MeO PEG (750) + 5PO 2:1 12 6 8 MeO PEG(750) + 8PO 2:1 13 7 9 MeO PEG (2000) + 5PO 2:1

EXAMPLES 14 TO 19 Preparation of Aqueous Paints

Pigment dispersion were prepared by milling a mixture of transparent rediron oxide pigment (389.08 parts Cookson Red AC 1005 ex Cookson),Dispersant 31.13 part), Humectant GRB2 (39.96 parts ex Avecia), ProxelBD20 biocide (1.06 parts ex Avecia), Densil P fungicide (1.06 pars exAvecia), 0.12 parts Rhodaline 6681 defoamer (ex Rhodia) and water(245.13 parts) in a Dispermat SL mixer at 36° C. for 1 hour in thepresence of 1 mm diameter glass beads (560 parts). The beads were thenseparated and paints prepared by diluting 8 parts dispersion with 4parts water and mixing this diluted dispersion with a (80:20) mixture ofan alkyd resin (Setal 6306 SS-60 ex Akzo Nobel) and melamineformaldahyde resin (Cymel-350 ex Dyno-Cytec) (8 parts) diluted withwater (4 parts). The resultant paint was applied to a Black/White cardby K-bar to give a film thickness of 100 microns. The paint was allowedto dry for 30 minutes and then baked at 120° C. for 30 minutes. Theglass and haze of the aqueous paints are recorded below in Table 4.TABLE 4 Gloss Example Dispersant 60° 20° Haze 14 3 91.0 63.9 339 15 497.8 89.2 93 16 5 96.2 83.0 170 17 6 96.9 78.4 215 18 7 96.5 81.2 182 198 97.8 88.0 97

EXAMPLES 20 AND 21 WITH COMPARATIVE EXAMPLES G and H Effect ofOverphosphation

Examples 14 to 19 were repeated except that the dispersion used as amillbase made using Cookson Red AC 1000 (77.83 parts), Dispersant (6.23parts), Humectant GRB2 (8.00 parts), Rhodaline 6681 (0.1 parts) andwater (49.34 parts).

The results are given in Table 5 below. In these examples the degree ofphosphation of the polyether MeO PEG (550)+3PO has been varied. TABLE 5Ratio of P to Gloss Example Polyether 60° 20° Haze % Transparency G  1:1.25 76.6 40.1 352 0 H 1:1 80.2 48.2 301 −4 20 1.3:1   89.3 67.2 269+3 21 2:1 94.2 76.4 216 +3-4

Footnote to Table 5

Comparative Examples G and H contain a high ratio of polyether chain toPhosphorus, e.g. the ratio of each phosphorus atom of the phosphatingagent to polyether in Example G is 1:1.25.

Examples 20 and 21 contain a high ratio of phosphorus atom of thephosphating agent to each polyether chain, e.g. the ratio of phosphorusatoms in the phosphating agent to polyether chain in Example 20 is1.3:1.

These examples clearly show that the gloss is increased by using ahigher ratio of phosphating agent to polyether chain. These dispersantsare thought to contain a pyrophosphate moiety

The transparency of the resultant paint films has also been comparedusing Comparative Example G as internal control. Those paints containingan overphosphated dispersant exhibit higher transparency than thosewhich are underphosphated as described in EP 863795.

The viscosity of the dispersions used as millbases in Examples 20 and 21and Comparative Examples G and H have also been measured at 20° C. usinga TA Instruments Viscometer fitted with a 2 cm steel plate at a 50micron gap. The viscosity at a shear rate of 37.6 sec⁻¹ is given inTable 6. TABLE 6 Ratio of P to Polyether Viscosity (Pas)   1:1.25 3.8891:1 1.639 1.3:1   0 2:1 0

The data in Table 6 shows that the overphosphated dispersants exhibitsignificantly lower viscosity compared with the dispersants made asdescribed in EP 863795.

EXAMPLES 22 AND 23 WITH COMPARATIVE EXAMPLES

The Dispersant was dissolved in a 4:1 mixture of methoxy propylacetateand n-butanol in the amounts shown in Table 5 below, with heating asnecessary. After cooling to 20° C., 3 mm diameter glass beads (17 parts)were added together with pigment and the mixture was milled in ahorizontal shaker for 16 hours. The beads were then removed and thefluidity of the resulting dispersion was assessed using an arbitraryscale A to D (good to poor). The results are given in Table 7 below.TABLE 7 Amount Amount Amount Exam- Dis- Amount of of Red of White of plepersant Dispersant Pigment Pigment Solvent Fluidity 22 1* 0.25 3 6.75 A23 1 0.25 3 6.75 A L I 0.25 3 6.75 C 24 1 0.25 3.5 6.25 A/B M I 0.25 3.56.25 D 25 1 0.25 4 5.75 B 26 1* 0.2 7.5 2.3 A 27 1 0.2 7.5 2.3 A N I 0.27.5 2.3 B 28 1 0.15 7.5 2.35 A  0 I 0.15 7.5 2.35 B 29 1 0.1 7.5 2.4 B PI 0.1 7.5 2.4 C 30 1 0.2 7.5 1.8 D Q J** 0.19 7.5 2.3 B R K** 0.19 7.52.3 B

Footnote to Table 7

Red Pigment is Sicotrans Red L2817 ex BASF

White Pigment is Tioxide TR92 ex Tioxide

Dispersant 1* is the free acid form of Dispersant 1 described in Example1 prior to converting to the diethanolamine salt.

Dispersant I is identical to Dispersant 1 except that the ratio ofphosphorus atom in the phosphating agent to polyester chain is 1:1.25 asdescribed in U.S. Pat. No. 6,197,877.

Dispersant J** contains 0.19 parts Dispersant I with 0.01 partspolyphosphoric acid.

Dispersant K** contains 0.19 parts Dispersant I with 0.01 parts orthophosphoric acid.

The results in Table 7 clearly show that the dispersants having a highratio of phosphorus atoms relative to the polyester chain made accordingto the invention given more fluid dispersions than those using adispersant made according to U.S. Pat. No. 6,197,877 which contain a lowratio of phosphorus atoms to polyester chain. Comparative examples Q andR show that the higher fluidity of Examples 26 and 27 is notattributable to either free pyrophosphoric acid or free ortho phosphoricacid.

1. A dispersant which comprises the reaction product of a phosphatingagent and a compound of formula 1R—OH  1wherein the ratio of each atom of phosphorus in the phosphatingagent to the compound of formula 1 is not less than 1.3:1, includingmixtures and salts thereof; and wherein R is a residue of a polyesterand/or polyether having a polymerisation terminating group:
 2. Adispersant as claimed in claim 1 wherein the ratio of each atom ofphosphorus in the phosphating agent to the compound of formula 1 is notless than 1.8:1.
 3. A dispersant as claimed in claim 1 wherein the ratioof each atom of phosphorus of the phosphating agent to each compound offormula 1 is not greater than 3:1.
 4. A dispersant as claimed in claim 1wherein the phosphating agent is either P₂O₅ or polyphosphoric acid. 5.A dispersant as claimed in claim 1 wherein the number-average molecularweight of R—OH is not less than
 200. 6. A dispersant as claimed in claim1 wherein the number-average molecular weight of R—OH is not greaterthan 10,000.
 7. A dispersant as claimed in claim 1 wherein the polyesterand/or polyether moiety of R—OH is attached to the polymerisationterminating group via an amino, mercapto or preferably a hydroxy group.8. A dispersant as claimed in claim 1 wherein the compound of formula 1is a compound of formula 2TO-(CO-A-O)_(n)(BO)_(m) H₂ wherein T is a polymerisation terminatinggroup; A is C₁₋₃₀-alkylene or C₂₋₃₀-alkenylene; B is C₂₋₄-alkylene; nand m are each, independently, from 0 to 500; and n+m is not less than4; including salts and mixtures thereof.
 9. A dispersant as claimed inclaim 8 wherein (CO-A-O)_(n) is the residue of two or more differenthydroxy carboxylic acids or lactones thereof.
 10. A dispersant asclaimed in claim 8 wherein (B-O)_(m) is the residue of two or moredifferent alkylene oxides.
 11. A dispersant as claimed in claim 8wherein T is aryl, heteroaryl, aralkyl, cycloalkyl or alk(en)yl whichmay be linear or branched and where T may be optionally substituted. 12.A dispersant as claimed in claim 8 wherein T contains not greater than50 carbon atoms.
 13. A dispersant as claimed in claim 8 wherein T isphenyl or naphthyl optionally substituted by C₁₋₂₀-alkyl (linear orbranched), C₁₋₁₂-alkoxy (linear or branched) or phenoxy; or C₁₋₃₆-alkylwhich may be linear or branched and optionally substituted by halogen orC₁₋₆-alkoxy.
 14. A dispersant as claimed in claim 8 wherein (CO-A-O)_(n)is derived from glycolic acid, 5-hydroxy valeric acid, 6-hydroxy caproicacid, ricinoleic acid, 12-hydroxystearic acid, 12-hydroxy dodecanoicacid, 5-hydroxy dodecanoic acid, 5-hydroxy decanoic acid, 4-hydroxydecanoic acid, β-propiolactone, δ-valerolactone, ε-caprolactone orC₁₋₆-alkyl substituted ε-caprolactone including mixtures thereof.
 15. Adispersant as claimed in claim 8 wherein (B-O)_(m) is derived frompropylene oxide, ethylene oxide or butylene oxide, including mixturesthereof and preferably ethylene oxide alone.
 16. A dispersant as claimedin claim 1 which is a salt of an alkanolamine.
 17. A process for makinga dispersant as claimed in claim 1 which comprises reacting a compoundof formula 1R—OH  1 wherein R is a residue of a polyester and/or polyether having apolymerisation terminating group: with a phosphating agent at atemperature from 40° C. to 120° C. wherein the ratio of each phosphorusatom of the phosphating agent to the compound of formula 1 is not lessthan 1.5:1.
 18. A composition comprising a particulate solid and adispersant as claimed in claim
 1. 19. A composition as claimed in claim18 which additionally comprises a liquid medium.
 20. A composition asclaimed in claim 18 which additionally comprises a plastics material.21. A composition as claimed in claim 20 wherein the plastics materialcomprises an unsaturated polyester resin or an acrylic resin.
 22. Amillbase, paint or ink comprising a particulate solid, film-formingbinder resin, liquid medium and a dispersant as claimed in claim 1.